Ask architects what they do: they'll share lofty stories and philosophy. Louis Kahn told us to ask a brick what it wants to be. Watch what architects actually do: all of them draw. They draw, doodle, trace, and draw, and draw, and draw some more.
We draw to get some inspiration out of our head and onto paper. This action changes the cognitive work from imagination to perception.
Once on paper the truths about reality push back on imagination. With real, linear geometry in front of us, the pieces don't fit together quite as we imagined.
We tear off another sheet of tracing paper to try different shapes, different proportions, different placement. New inspiration and new frustration both grow from this dialog between imagination and paper. There is no shortcut.
What is in the designer's head changes as the paper pushes back. Eventually a compromise is found to be good enough.
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My formal training was in architecture. But my brother was the artist in the family. I had to learn to draw. A vivid college memory: it was late in the semester. The instructor wandered by my desk while I was staring out the window to ask me how things were going. I talked and talked about the ideas bouncing around in my head, twirling a lead holder in my fingers. "Why don't you draw more and think less?" he asked.
Inspired by ruins, DNA and primary geometry, Louis Kahn was one of the 20th century's most influential architects. Why isn't he more famous? Oliver Wainwright on the life and legacy of a man who died bankrupt. Louis Kahn: the brick whisperer. The Guardian. article 
Louis Kahn used to tell his students: if you are ever stuck for inspiration, ask your materials for advice. "You say to a brick, 'What do you want, brick?' And brick says to you, 'I like an arch.'"